I need to write Hangouts Bot which will delete all messages from the chat/room and after this send new one message. Hangout API provides a possibility to delete just one message by one request (with a known identifier).
I wrote .sh file with the next code (sending message):
curl -X POST \
-H 'Content-Type: application/json' \
'https://chat.googleapis.com/v1/spaces/SPACE_ID/messages' \
-d '{"text": "Message!"}'
How can I delete all messages from the chat before sending a new one? (by Hangouts API)
As you said, the delete method requires a message ID and only deletes one message. There is a get method but it doesn't support returning all messages. If all of the messages you are deleting were generated by the bot itself I would suggest that you keep a running log of the message IDs and use that to delete them. I do not believe a bot can delete a message generated by another user or a bot other than itself just as a user can't delete another user's message.